Frequency controlling and regulating means for mechanical oscillators



C. F. CLIFFORD FREQUENCY CONTROLLING AND REGULATING March 7, 1961 MEANS FOR MECHANICAL OSCILLATORS Filed May 7, 958

United States Patent 2,973,619 FREQUENCY CONTROLLING AND'REGULATING MEANS FOR MECHANICAL OSCILLATORS Cecil Frank Clifford, Bath, England, assignor to Horstm'ann Clilford Magnetics Limited, Bath, Somerset, England, a British company Filed May 7, 1958, Ser. No. 733,689

priority, application Great Britain May 9, 1957 Claims. c1; 58-116) This invention relates" to frequency controlling and regulating means for mechanicaloscillators and is par ticularly, though not exclusively, applicable to magnetically coupled rotary and oscillatory systems which are coupled by means of a: wavy magnetic path and complementary polar formations; For example, the invention is equally applicable to a permanent magnet oscillator for modification of its frequency to provide a standard frequency device much cheaper than a quartz crystal oscillator with its dividing circuits.

The present invention is also particularly, though not exclusively,-applicable to escapements for time pieces and is an improvement in, or development of the invention, the subject of my Patent No. 2,787,115. Research with the construction of mechanism described in the specification of the earlier patent aforesaid has shown that a regulator which is movable transversely of the oscillating part, so as to vary the magnetic coupling with such part without varying the air gap, enables frequency regulation to be obtained with less interference with isochronism and with a nearer linear characteristic than where the air gap itself is varied by the movement for adjustment. For this reason the arrangement of Fig. 2 of the patent aforesaid has appreciable advantages over certain other arrangements but the overall length of the mechanism of Fig. 2, measured in the direction of the axis of the regulating screw, limits the use of such arrangement. This limitation applies particularly to wrist watches which have only about .10 inch available in the aforesaid direction.

With the aforesaid features in mind the object of the present invention is a frequency controlling and regulating means, for magnetically coupled rotary and oscillatory systems, having an improved construction and arrangement of parts.

According to the invention, the improved frequency controlling and regulating means for mechanical oscillators comprises a helix of magnetic material, magnetically coupled to a moving part of the oscillatory system and rotatably mounted about, and with its axis substantially normal to, the path of oscillation of such part, whereby rotation of the said helix about its axis, without axial movement, traverses an effective portion thereof relative to the said part of the oscillatory system to vary the magnetic coupling.

In the accompanying drawing:

Fig. 1 is a diagram showing one example of a frequency controlling and regulating device made in accordance with the present invention with the device shown in its position of minimum magnetic coupling with the oscillatory system.

Fig. 2 is a similar diagram showing the device turned to its position of maximum magnetic coupling.

Fig. 3 is a perspective view of a portion of the magnetic escapement mechanism, showing the rotor and associated parts.

As shown, a is a frame member of a time piece having a magnetic escapement of which only the inwardly turned pole ends b of a magnet are shown. Such escapement may, for example, be the same as described and illust'rated inter alia, in my earlier Patent No. 2,787,115.

The frequency controlling and regulating device comprises a helix c having the form of a single turn, singlestart quickpitch'square thread screw formed on the periphery of a body d of magnetic metal, such as soft iron. The ends of the helix-are finished to lie in a radial plane normal to the axis of the helix but otherwise the helix is of regular pitch and uniform cross section. Such body is adjustably secured by means of a grub screw e to a stem 1 having a screw head g. A spring h operates as a friction device to prevent accidental rotation and also to hold the device in its preset axial relation to the magnet poles. As can be seen, the device is arranged with its axis normal to the plane of oscillation and symmetrically of the amplitude of oscillation of the poles and presenting the helix relatively to one pole only.

In use, with the helix in the position shown in Fig. 1 relative to the N pole of a magnetic oscillator it is in its position of minimum magnetic coupling because the portion of the helix presented to the oscillator is at a position of maximum lateral displacement relative to the N-S air gap of the oscillator poles, though it must draw some leakage flux therefrom. Rotation of the device g in effect causes the helix to traverse relative to the magnet poles so that the effective portion of the helix immediately. facing the poles is brought nearer to the working. gap between them and therefore attracts more magnetic flux to augment the returning force of the mounting spring of the magnet which determines its frequency. Rotational movement increases or decreases the magnetic coupling according to the direction of traverse movement of the helix relative to the inwardly turned pole end of the magnet without altering the air gap.

In Fig. 3 of the drawings I have shown a spoked magnetic escape wheel 1 providing a wavy magnetic track. This wheel is rotatably mounted in the frame member a and a second frame member In spaced therefrom, and extends between the poles of the oscillating magnet b so that the latter in their oscillations follow the wavy magnetic track on the wheel I of disklike form. The screw a is mounted upon one side of the escape wheel, and, as illustrated, is disposed adjacent the north pole of the magnet. I

It is noticeable, of course, that the effective portion of the helix is inclined to the plane of oscillation, which inclination might be expected to have an adverse influence in that one excursion of the magnet poles to and from the repose position might occur in say 0.3% less time than the other excursion from the repose position. Any such influence, if it exists, does not appear to have measurably harmful effects nad hence appears to be negligible. Such effect can, of course, be cancelled out by providing a second device with opposite hand of spiral and therefore relative opposite traverse associated with the other pole of the oscillator magnet, but for practical reasons, this is not easy to provide and would seem to be unnecessary for ordinary purposes.

One of the advantages of the arrangement above described is that it gives substantially linear adjustment, e.g. 1 minute/ day regulation for each 10 turning of the screw. If it were desired to make this linearity closer still, then the diameter of the helix could be made differout throughout its length so that the air gap is varied slightly as the helix traverses the face of its magnetically complementary member. Alternatively, it will be obvious to those skilled in the art that the helix or pole end could be otherwise shaped to provide the feature of linearity, as, for example, by shaping the complementary end area of the pole end, or the axis of the helix could be inclined relative to the end of the magnet so that the air gap varies approximately as the helix is turned to progress the operating part of the helix relative to the end of the magnet.

The invention is obviously not limited to all the details of the example above g iven as modificationscan be made without departing from the scope of the invention. For instance, the helix could be mounted on a cylindrical body of non-magnetic material. The width, diameter and distance of the helix from the pole and the magnetic properties of the material of which it is made will be determinable by the degree of control which it is desired to provide, and the elfects which it is desired to produce, with relation, for example, to isochronism but the dimensional relations defined in Patent No. 2,787,115 may conveniently be adopted.

, I claim:

1. A frequency controlling and regulating means for a mechanical oscillator comprising a helix of magnetic material, magnetically coupled to a moving part of the oscillatory system, said helix being rotatably mounted about,

and with its axis substantially normal to, the path of 20 oscillation of such part, whereby rotation of the said helix about its axis, without axial movement, traverses an effective portion thereof relative to the said part of the oscillatory systern to vary the magnetic coupling therewith.

2.'A frequency controlling and regulating means for an escapement mechanism of the kind comprising rotary and oscillatory systems coupled by means of a wavy magnetic path, preferably of metal of low hysteresis and complementary polar formations of a permanent magnet comprising a helix of magnetic material, magnetically coupled to a moving part of the oscillatory system, said helix being rotatably mounted about, and with its axis substantially normal to, the pathfof oscillation of such part, whereby rotation of the said helix about its axis, without axial movement, traverses an effective portion thereof relative to the said part of the oscillatory system to vary the magnetic coupling therewith.

3. A frequency controlling and regulating means according to claim 2 characterised in that the oscillatory system comprises a magnet complementary to an annular wavy track on the rotary system and in that the helix is cylindrical and is located symmetrically of the amplitude of oscillation of the poles of the magent.

v 5. A frequency controlling and regulating means ac cording to claim 3 further characterised in that the magnet has inwardly turned end portions and the helix is in theform of a square section screw thread with a cylindrical periphery presented to the end of one of the said 25 inwardly turned ends of the magnet.

References Cited in the file of this patent UNITED STATES PATENTS Clifford May 1, 1956 2,787,115 Clifford Apr, 2, 1957 

